This invention relates to an improved, installation displacement contact and to an electrical connector employing such a contact. The invention has particular application to electrical connectors for terminating a coaxial cable. The contact of this invention is particularly suited for use in a connector for application to a printed circuit board.
Reference is hereby made to two copending applications assigned to the same assignee as this application; "IDC Termination For Coaxial Cables" by Leonard Feldberg, Ser. No. 557,771, filed on Nov. 14, 1983, and "IDC Termination For Coaxial Cable Having Alignment and Stabilizing Means" by H. Blackwood Ser. No. 553,833, filed on Nov. 21, 1983. These cross-referenced applications are incorporated herein by reference in their entirety.
Electrical connectors employing insulation displacement contacts are well known in the art and are commercially available from companies, such as Burndy Corporation, Norwalk, Ct. By using insulation displacement contacts, it is unnecessary to strip the insulation from the wire to be contacted. The contact has a blade-like configuration with a slot having a width corresponding to the diameter of the electrical conductor. When the insulated wire is pressed into the slot, the edges of the slot displace the insulation to allow intimate electrical contact between the conductor and the slot edges. The use of such insulation displacement contacts in a wide variety of electrical connectors is illustrated by reference to U.S. Pat. Nos. 3,112,147, 3,118,715, 3,434,093, 3,617,983, 3,772,635, 3,835,444, 3,836,944, 3,842,392 and 3,848,951. In some of the connectors illustrated in these patents, the insulation displacement contact includes two contact slots in axial alignment which are electrically connected to provide a redundant contact to the conductor.
In prior art insulation displacement contacts, the slot into which the conductor is pushed to make electrical contact has a width dictated by the tooling used to manufacture it. The width of the slot cannot be readily changed due to the nature of the tooling which is very expensive. The tooling employed usually requires a series of steps that begins with a blank metal strip in order to form the insulation displacement contact. This problem is overcome, in accordance with this invention, by modifying the insulation displacement contact so that the width of the slot can be readily varied such as by one additional step of the manufacturing process. The tooling can, therefore, provide one basic insulation displacement contact and, then, in one last step, shape the contact to provide the exact width of the slot desired.
The adjustable slot width insulatio;n displacement contact of this invention is particularly applicable for terminating a coaxial cable. Coaxial cables generally come in a wide range of diameters. The coaxial cable can comprise a single strand cable or a ribbon-type cable. In a coaxial cable, the central conductor is shielded from outside interference by a surrounding conductor which is spaced therefrom. An insulating layer separates the surrounding shield and the central conductor. An insulating jacket, in turn, surrounds the shield. The shield may be braided, metallic wire or foil, etc. When the shield comprises a foil, it is known to utilize a drain wire in contact therewith for terminating the foiled shielding.
Ribbon-type coaxial cables including a plurality of individual cable elements with a common outer insulating jacket are also known. As for example, the ribbon coaxial cables described in U.S. Pat. Nos. 3,963,319 to Schumacher and 4,035,050 to Volinskie. These patents also disclose electrical connectors for terminating the ribbon-type cable to a printed circuit board. The cables described in these patents employ a center conductor and drain wire lying parallel to one another. The electrical contacts of the connector are connected to the respective conductors and the wires are laterally displaced from one another. The result is an electrical connector assembly of substantial width since the contacts of the connector are spaced laterally for connection to parallel drain and central conductors.
An ordinary coaxial cable generally employs a braided shield. With respect to such cables, considerable difficulty and time is consumed in assemblying them to circuit boards. Further, the manner in which the cables must be stripped to reveal the shield and conductors can result in a mismatch of impedance. In accordance with the prior art approach, the insulation around the braid is cut quite far back. The braid is then combed out and cut back somewhat less than the outer insulating jacket to expose the insulation around the conductor. The insulation around the conductor is then cut back about midway between the end of the braid and the end of the conductor to expose the conductor. The conductor is terminated to the circuit board and the braid is "pig-tailed" and then joined to the circuit board.
Several problems exist in this prior art approach. The braid and the center conductor can be nipped during stripping thereby deteriorating the performance of the cable. Also, since the braid is cut back more than the central conductor, there is an impedance mis-match and this can produce a distorted signal. Obviously, the prior art process, being a multiple step manual one, is extremely time consuming and slow.